This invention relates to multi-speed planetary transmissions for use in vehicles and, more particularly, to multi-speed planetary transmissions having six or more forward speed ratios.
Passenger vehicles include a powertrain that is comprised of an engine, multi-speed transmission and a differential or final drive. The multi-speed transmission increases the overall operating range of the vehicle by permitting the engine to operate through its torque range a number of times. The number of forward speed ratios that are available in the transmission determines the number of times the engine torque range is repeated. Early automatic transmissions had two speed ranges. This severely limited the overall speed range of the vehicle and therefore required a relatively large engine that could produce a wide speed and torque range. This resulted in the engine operating at a specific fuel consumption point, during cruising, other than the most efficient point. Therefore, manually-shifted (countershaft) transmissions were the most popular.
With the advent of three- and four-speed automatic transmissions, the automatic shifting (planetary gear) transmission increased in popularity with the motoring public. These transmissions improve the operating performance and fuel economy of the vehicle. The increased number of speed ratios reduces the step size between ratios and therefore improves the shift quality of the transmission by making the ratio interchanges substantially imperceptible to the operator under normal vehicle acceleration. It has been suggested that the number of forward speed ratios be increased to five and even six speeds. This has been accomplished in many heavy truck powertrains. Six-speed transmissions are disclosed in U.S. Pat. No. 4,070,927 issued to Polak on Jan. 31, 1978, U.S. Pat. No. 6,071,208 issued to Koivunen on Jun. 6, 2000, and U.S. Pat. No. 5,106,352 issued to Lepelletier on Apr. 21, 1992.
Six-speed transmissions offer several advantages over four- and five-speed transmissions, including improved vehicle acceleration and improved fuel economy. While many trucks employ power transmissions, such as Polak, having six or more forward gear ratios, passenger cars are still manufactured with three- and four-speed automatic transmissions and relatively few five- or six-speed devices due to the size and complexity of these transmissions. The Polak transmission provides six forward speed ratios with three planetary gear sets, two clutches and three brakes. The Koivunen patent utilizes six torque transmitting devices including four brakes and two clutches to establish the six forward speed ratios and another reverse ratio. The Lepelletier employs three planetary gear sets, three clutches and two brakes to provide six forward speeds. One of the planetary gear sets is positioned and operated to establish two fixed speed input members for the remaining planetary gear sets.
It is an object of the present invention to provide an improved family of multi-speed transmissions each having three planetary gear sets and five selectively engageable torque transmitting mechanisms.
In another aspect of the present invention, one of the planetary gear sets has a member continuously connected with an input shaft, another member continuously connected with an output shaft, and a further member non-continuously connected. In another aspect of the present invention, two of the planetary gear sets have two members thereof continuously interconnected. In yet another aspect of the present invention, one of the planetary gear set having two interconnected members has a third member continuously connected with a stationary member such as the transmission housing and the other of the planetary gear sets has a non-continuously connected member.
In still another aspect of the present invention, the five torque transmitting mechanisms are all selectively engageable rotating torque transmitting mechanisms (clutches). In a further aspect of the present invention, the clutches are selectively engaged in combinations of two to provide at least six forward speed ratios and a reverse ratio.
The present invention defines a family of transmission wherein each family incorporates three planetary gear sets and five rotating torque transmitting mechanisms to establish a compact structure having minimum mechanical content to provide six forward speed ratios and a reverse ratio between an engine driven input shaft and an output shaft. Another of the planetary gear sets has three rotatable members with another member continuously connected with the input shaft, another member continuously connected with the output shaft and a further member that is non-continuously interconnected. Another and a further of the planetary gear sets each has three members with respective first members being continuously interconnected and respective second members being continuously interconnected through first and second continuous interconnections, respectively. The third member of the other planetary gear set is non-continuously connected and the third member of the further planetary gear set is continuously connected with a stationary member such as a transmission housing.
The five rotating torque transmitting mechanisms are rotating-type mechanisms that are selectively engaged to provide further interconnections between members of the planetary gear arrangement. A first of the torque transmitting mechanisms selectively interconnects one of the continuous interconnections with either the input shaft, the output shaft, or the non-continuously connected member of one of the planetary gear sets. A second of the torque transmitting mechanisms selectively interconnects one of the continuous interconnections with either the input shaft, the output shaft, or a non-continuously connected member of one of the planetary gear sets. A third of the torque transmitting mechanisms selectively interconnects one of the continuous interconnections with either the input shaft, the output shaft, or the non-continuously connected member of one of the planetary gear sets. A fourth of the torque transmitting mechanisms selectively interconnects the first continuous interconnection, the second continuous interconnection, or the non-continuously connected member of one of the planetary gear sets with either the input shaft or the output shaft. A fifth of the torque transmitting mechanisms selectively interconnects one of the non-continuously connected members or one of the continuous interconnection with either the input shaft, the output shaft, or the other of the non-continuously connected members.
The planetary gear sets include a sun gear member, a ring gear member, and a planet carrier assembly member. Each of these can be defined as the first, second or third member in a specific family member. The planet carrier assembly member can have a plurality of pinion gears meshing with both the sun gear member and the ring gear member (simple planetary) or a plurality of intermeshing pinion gears meshing with the sun gear member and the ring gear member, respectively (compound planetary). Each family member has at least one simple planetary gear set while the other two planetary gear sets may be either of the simple or compound type of planetary gear set.